(CNN)Bodies piled upon bodies. A few people still moving while others appear lifeless. Rescue workers struggling to reach those still alive by pulling the dead out of the way.

A day after a deadly crush killed 717 people during Hajj in Saudi Arabia, a major question remained Friday: what caused the chaotic stampede that killed throngs of pilgrims?

Saudi officials are trying to figure out what went horribly wrong this week during the annual Islamic pilgrimage to Mecca. But some who made the journey said various factors may have played a role.

Too many people, too little time

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More than 2 million Muslims from around the world are in Saudi Arabia for Hajj, a pilgrimage that every Muslim who has the financial means and the physical ability to must make. For most, it is the spiritual climax of their lives, with many saving for decades to make the journey.

And the millions of people must perform a litany of rituals in five days, including the symbolic stoning of the devil in Mina — about 2 miles away from Mecca.

That’s where Thursday morning’s deadly stampede took place, killing 717 people and injuring 900 more. Thursday was day three of the five-day Hajj.

“There’s so little time to complete the rituals, Hajj pilgrim Ethar El-Katatney said.

Journalist Khaled Al-Maeena said he believes pilgrims rushing to finish could have been the main reason for the stampede.

“People like to do the first stoning in the morning,” he told CNN from Jeddah, Saudi Arabia.

Extreme heat and exhaustion

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The journey is physically grueling enough on its own.

But with temperatures soaring over 43 degrees Celsius (110 degrees Fahrenheit), anyone who succumbs to the elements might collapse and never recover, El-Katatney said.

“I was out for a couple of hours just kind of taking photos, recording. And just two hours standing in the sun makes you so dizzy and so incredibly faint,” she said from Mina.

“But regardless, people were still continuing to … their ritual, where the stampede happened.”

“It’s literally a pile of bodies of people who … pushed, they shoved, they panicked, they screamed,” she said. “It was hot, someone fell, others trampled and they got stampeded.”

El-Katatney said she talked to some of the men who were caught in mayhem.

“They told me how if you fell, if you weren’t strong enough to withstand the pushing and shoving … if you fell, you weren’t going to get up again.”

Inexperience and confusion

Even though Saudi officials are extremely versed in hosting Hajj crowds, many of the pilgrims are making the journey for the first time — and might not be prepared to follow all directions or handle the chaos.

Maj. Gen. Mansour Al-Turki, the interior ministry’s security spokesman, hinted that the problem may have stemmed from the noncompliance of some pilgrims to follow established guidance, the Saudi Press Agency reported.

“They could go on their own, or try to take a shortcut,” journalist Jamal Khashoggi of the Saudi El Arab TV told CNN.

Moving in opposite directions

El-Katatney said pilgrims were trying to push their way in opposing directions — some headed to the site of the stoning, some coming back from their previous ritual.

After the stampede, it took hours for rescue workers to try to tend to all those trampled.

“The ambulances, the sirens were overwhelming. For hours and hours, you could hear them constantly.”

The incident is the deadliest disaster at Mina since 1990, when 1,426 people died.